Subaqueous tunneling



April 11, 1939.

F. DONALDSON SUBAQUEOUS :TUNNELING Filed March 9, 1938 r 3 Sheets-Sheet l INVENTOR ATTORNEY April 1 1, 1939. F. DONALDSON SUBAQUEOUS TUNNELING s Sheets-Sheet 2 n H .H

INVENTOR Filed March 9, 1938 7A g g z BY z ATTORNEY April 11, 1939. F. DONALDSON 2,154,233

SUBAQUEOUS TUNNELING Filed March 9, 1938 3 Sheets-Sheet 3 INVENTOR mu H ATTORNE Patented Apr. 11, 1939 UNITED STATES PATENT OFFICE SUBAQUEOUS TUNNELING Application March 9, 1938, Serial No. 194,782

9 Claims.

In Patent 1,883,622, issued October 18, 1932, the undersigned described a method for lowering the hydrostatic head of the ground water in connection with the driving of subaqueous tunnels under compressed air in permeable ground, and explained the reasons for and advantages of such a reduction. The method and apparatus hereinafter described are applicable to the reduction of this hydrostatic head when the material beneath the river bottom is such that the influence of wells on the banks can not be felt far beneath the river, or where the river is too wide, or else where the banks of the river are of rock or other impermeable material which makes the use of drainage walls on the banks partially or entirely ineffective.

The utility of the present improvements is not restricted, however, to the existence of the conditions just referred to, but are generally applicable for reduction of hydrostatic head of the water in the ground and the correlative air pressure in the driving of subaqueous tunnels in permeable material. An advantage of the improvements is that the hydrostatic head can be reduced more efiectively than before along the course of the tunnel, and especially at the middle portion beneath the bed of the river, or that is to say, farther out in the river from the river banks. It is to be understood that the term river includes any body of water beneath which such a tunnel might be driven.

In the present invention, reduction in hydrostatic head affecting the main tunneling operation is greatly facilitated by the provision of one or more drainage channels extending in the ground or tapping from the ground in regions which parallel the main tunnel to be driven. It is to be understood that the term parallel is not used in an exact sense. Without limitation as to particular direction, the drainage channels, with or without appurtenances such as well points or collector points, are arranged to extend in the vicinity of, but not necessarily adjoining, the course of the main tunnel or tunnels, and outward from the banks beneath the river. The water entering these drainage channels maybe delivered into shafts, caissons or the like, from which it is discharged; or the drainage channels may be connected directly to the suction sides of pumps to increase the de-watering rate; or the drainage water may be removed in other manner.

As in my prior patent, it is highly desirable to reduce or prevent overhead infiltration from the river by establishing or providing on the river bottom an artificial or natural blanket of clay.

silt or other material, this impervious or semiimpervious blanket, covering, or matte preferably extending over the main tunnel and over and laterally up and down stream beyond the drainage channels. The blanket may be produced by drainage or pumping, causing a down-draft through the river bottom, with the result that silt in the river water seals, toa useful degree, the bed of the river; or it can be made by depositing clay or the like, or even by applying a relatively impervious membrane. sense need not necessarily be resorted to, since the efiluent from the drainage channels may be removed in any suitable manner.

In the accompanying schematic drawings forming part hereof, and in which like reference char acters indicate similar parts in different views:

Fig. 1 is a view somewhat in the nature of a vertical section transverse to a river, illustrating one form of execution of the invention;

Fig. 2 is a schematic view taken parallel with the river, as if on the section line 2-2;

Fig.3 is a View similar to Fig. 1 but illustrative of another form of the invention;

Fig. 4 is a view bearing the same relation to Fig. 3 as Fig. 2 does to Fig. 1, and may thus be considered as if it were a section on the line 4-4 of Fig. 3;

Fig. 5 is a schematic cross-section of one of the drainage tunnels and drainage pipes of Figs. 3 and 4;

Fig. 6 is a view of the order of Figs. 1 and 3, and representing another form of the invention;

Fig. 7 is a view suggestive of a section taken on the line l-l of Fig. 6; V

Fig 8 is a detail in the nature of a cross-section of one of the drainage tunnels of Fig. 7, with drainage headerand a well point or collector point;

. Fig. 9 is another of the series of views like Figs. 1, 3 and 6, showing another way of carrying out the invention;

Fig. 10 is a schematic view resembling a section on the line I 0|0 of Fig. 9; Figs. 11 and 12 are views similar to Figs. 1 and 2 and like views, showing still another embodiment of the invention, Fig. 12 being in the nature of a section on the line l2l2 of Fig. 11;

Fig. 13 is a view taken as if in section crosswise of the river, showing other embodiments; and

Figs. 14 and'15 are in the nature of sectional views taken on the lines l4-l4 and I 5-| 5, re-,

spectively, of Fig. 13.

In Figs. 1 and 2, and in other views, the river Pumping in a specific is shown at 2, the main tunnel to be driven is indicated at 3. This tunnel represents either a single tunnel or a plurality of tunnels. At the banks of the river, or at available locations, water-tight shafts or caissons 4 are sunk, or existing wells or reservoirs may be used. As shown in Fig. 2, and in other views, there are two drainage shafts at each side of the river, but in certain cases only one may be provided. The shafts illustrated are arranged at opposite sides of and spaced from the course of the main tunnel 3. Obviously, the drainage shafts may be located either on the banks of the river or in the river channel.

From the drainage shafts in Figs. 1 and 2, one or more slotted or perforated screen pipes 5, made up of sections, are jacked or otherwise projected into the ground, to or toward the midregion beneath the river bed. Such drainage channels are generally parallel with the path of the main tunnel thereafter to be driven or to be completed. Depending upon the conditions of the work to be done, they may be inclined upward or downward or laterally, and they may be provided with branches, or they may be located fanwise beneath the main tunnel. They may be at, above or below the general level of the main tunnel. Their arrangement is such as to drain the ground beneath the river in effective relation to the operation of driving the main tunnel.

Fig. 2. shows. a group of three drainage pipes 5 extending from each shaft 3, this being illustrative. As shown at the left of Fig. 1, the screen pipes or drainage pipes deliver into the shafts 4, from which the drainage water is pumped by pumps 6, through uptake pipes l to the surface. and discharged into the river. At the right of Fig. 1, the drainage pipe or pipes are connected with the suction of av pump 6 which delivers water through pipes 1 to the surface; this increases the rate at which drainage water is removed and consequently the rate at which the ground near the main tunnel path can be de- Watered. In some instances the two arrangements may be employed in conjunction as illustrated. The drawings are also illustrative of optional means of disposal, either of which may be, employed to the exclusion of the other, both in this and in other forms of the invention.

In usual operation, one or more shafts or caissons, such as the shafts 4., are sunk before the main tunnel is driven under compressed air beneath the river, and the drainage channels 5 are also put in place at this time. A definite sequence need not be observed, since the drainage channels may be constructed with and ahead of; the construction of the tunnel proper.

With the aid of a blanket 8 applied to the river bottom, or created thereon, as hereinbefore described, extending lengthwise over the course of the main tunnel and drainage channels and also laterally, the removal of Water through the drainage channels reduces the hydrostatic head in the ground in the region affecting the driving of the main tunnel, and thereby reduces the required air pressure in the driving of the tunnel.

Figs. 3-5 illustrate the fact that slotted or perforated. drainage pipes 5 can be installed in open-bottom tunnels 9, driven under compressed air beneath the river. In this and other forms of the invention the drainage channels may be continuous from a shaft 4 at one side of the river to a like shaft at the opposite side, or they may extend toward the center beneath the river bed but not be continuous, see Fig. 1. Similarly, the drainage pipes may empty into the shafts, from which the water is pumped, or they may be connected to the pump suctions.

In Figs. 6, '7 and 8 enclosed drainage tunnels l0 are driven under compressed air between the shafts 4. Through openings in the bottom of these tunnels slotted collector points or well points H are projected down into the ground, these well points being preferably connected with headers I2 inside the tunnels, the headers either discharging into the shafts or being connected to the suctions of the pumps 6 The collector points may extend in other directions as dictated by conditions.

Figs. 9 and 10 illustrate a modification in which one or more large drainage pipes l2 are laid on or beneath the river bed, such pipes to be connected with the shafts or caissons 4, and, later, unwatered and provided with means for projecting well points or collector points ll through their bottoms, in order to collect water at a depth to be effective or from a favorable stratum.

In Figs. 11 and 12 drainage pipes 13 are laid upon the river bed, or in trenches dredged in the river bed, such drainage channels being preferably pipes with flexible joints laid from a cradle and being provided with suitable drainage openings. After the laying of these pipes they will be covered with coarse sand or gravel dumped or tremied from the water surface, and as in the various forms of the invention a blanket will be provided or formed as previously described.

In all of the foregoing forms of the invention the drainage channels either empty into shafts or caissons from which the water is pumped to the surface or river for disposal, or else the drainage channels are connected to the suctlons of pumps, which are shown inside the shafts though such pumps may be located wherever desired or convenient.

In Figs. 13-15 slotted or perforated drainage channels 5 are constructed from within access portions 3 of the main tunnel 3, instead of from special shafts or caissons sunk from the surface.

The access portions of the main tunnel are temporarily stopped at I4 while the drainage. channels. are being established. Adits I5 connect the partially constructed main tunnel, behind the stops M, with working chambers l6. Atthe left of Fig. 13 and in Fig. 14 the adits to the working chamber are in permeable ground, whereas at the right of Fig. 13 and in 15 the adits. are in rock or impermeable material, this being by way of illustration of different conditions that may be encountered. At the left of Fig. 13 and in Fig. 14 the working chamber is shown at approximately the same level as the main tunnel, while at the right of Fig. 13 and in Fig. 15 the working chamber is at a higher level. It will be understood that the two arrangements may be used in conjunction, or that either arrangement may be duplicated at both ends of the underriver region, depending on the particular situation. The working chambers are located laterally outward from the main tunnel, and from them the drainage channels 5 are projected to or toward the mid-region below the: river bed, or across from working chamber to working chamber. As in other forms of the invention, such drainage channels. may be projected through the permeable ground by the aid of jacking, boring methods or otherwise. The drainage water led intothe stopped-off sections of the main tunnel is removed through the constructed portions of the tunnel by pumping or in any suitable manner. Pumps 6' and pipes 1 are illustrated for the purpose.

In connection with the various forms of the invention it will be understood that the drained water is removed continually, though not necessarily uninterruptedly, during the construction of the main tunnel.

It will be apparent that, in all cases, the drainage channels, pipes or collector points should be so located as tobe outside the zone of air escaping from the main tunnel. In order that the flow of water from the drainage channels may affect the hydrostatic pressure in the main tunnel, the matte or blanket is provided as hereinbefore described to cover the bottom of the river over the area bounded by the drainage channels and extending laterally beyond them.

I claim:

1. In the construction of a subaqueous horizontally-extending tunnel driven under compressed air, the method which comprises installing horizontally-extending drainage channels: in permeable ground in the vicinity of and along the course of the tunnel to be driven, establishing a virtually Water-tight blanket or matte over the course of the main tunnel and over and beyond the drainage channels, and continually removing water collected by the drainage channels while the tunnel is driven beneath the body of water, thereby reducing the hydrostatic pressure on such tunnel and permitting a lower air pressure in driving it.

2. A method as set forth in claim 1, in which the drainage water is emptied from the drainage channels into shafts or caissons, from which the drainage water is discharged.

3. A method as set forth in claim 1, in which the rate of de-watering for the purpose of reducing hydrostatic pressure on the main tunnel is increased by connecting the drainage channels directly with pump suctions.

4. A method as set forth in claim 1, in which the drainage channels are projected from shafts or caissons.

5. A method as set forth in claim 1, in which the drainage channels are established in auxiliary driven tunnels.

6. A method as set forth in claim 1, in which drainage channels are provided with well points or collector points.

7. A method as set forth in claim 1, in which the drainage channels are pipes laid on or below the river bed.

8. In the construction of a horizontally-extending tunnel under a body of water at the bottom of which a virtually water-tight blanket or matte has been established overlying thecourse of the tunnel and the adjacent regions, the making of horizontally-extending passages under the matte on opposite sides of the course of the tunnel, and then lowering the static head of water in the ground along the course of the tunnel by withdrawing water through said passages from the regions adjacent said passages during the construction of the tunnel.

9. The method of reducing the hydrostatic pressure encountered in the construction of a tunnel through the ground from one side to the other of a body of water, which method comprises establishing two passages under the water on opposite sides of the course of the tunnel and extending lengthwise along the course of the tunnel, and withdrawing water from the ground below each of said passages through well points extending down from said passages into ground which is covered by a virtually water-proof matte.

FRANCIS DONALDSON. 

